Over the years many aids have been developed for blind people to compensate for the lack of visual reading ability which they no longer have. Of these many aids the most well known and most widely used is braille. In braille letters are represented by embossed characters made up of from one to six dots arranged in a configuration of two columns of three dots each. A blind reader touches braille characters with his fingers to identify the letters and words which he "reads". Since braille was first developed by Louis Braille in 1852, many blind persons have learned to read braille and numerous texts have been transcribed into braille. However, there are presently significant problems with providing and disseminating large numbers of braille copies of textual material due to several factors.
First, it is difficult or impractical to produce a large number of copies of most braille books. Most braille is written in grade 2 braille, which uses a kind of shorthand or speed writing to reduce the number of braille cells needed to transcribe the textual material to be read. Grade 2 braille includes many contractions and abbreviations for commonly used English words and phrases. While computer translators for converting English into grade 2 braille are now being developed, at the present time the vast majority of braille translations are provided by volunteers who are skilled in grade 2 braille and who produce braille pages using a manually operated six-key braille typewriter. This method has the disadvantage that only one copy may be made at a time. To make additional copies of such material, a thermal forming process may be used by which a polyvinyl choloride sheet is molded the paper page original to duplicate it. This process can only be done one page at a time which make the production of a braille copy of a book a very slow and tedious process. This process is also expensive since each sheet costs approximately 5 cents per sheet, in addition to the cost of the thermal forming equipment and any labor costs. While large quantities of braille pages may be produced by using a printing press modified to emboss braille on paper sheets using braille zinc plate masters, printing such braille pages is expensive because of the necessity of a modified printing press and the cost of producing braille zinc plate masters. Accordingly, it is economically impractical to use this process to produce small quantities of a book; and this process is limited to those textual materials having a wide potential readership.
Storing and distributing braille books is hindered due to the bulk of braille materials. Braille is typically embossed on sheets having dimensions of 11 inches by 111/2 inches. These sheets each contain 25 rows of 40 cells each. Text written in grade 2 braille requires, on the average, two sheets of braille for each single sheet of printed textual material. Thus, a 200 page book requires 400 pages of braille. When transcribed into braille a single book will require several individual volumes of braille pages. Each of these volumes is limited to approximately 100 braille pages by two factors. First, the embossed braille pages are thicker and require more room than flat printed pages. Second, braille pages must lie substantially flat when the volume is open in order to be capable of being read quickly and comfortably by a braille reader; and problems with binding braille pages together so that they will lie flat limits braille volumes to approximately 100 pages. The result is that textual material which can be conveniently contained within one or two ink-print books of reasonable size requires many braille volumes which are heavy and large in size.
Due to the large volume required by braille materials, many libraries are unable to maintain more than a few braille volumes on the shelves due to space restrictions. Blind students, who require several different books for their different classes, also have difficulty in carrying around the many bulky braille volumes required to transcribe each textbook.
Several systems have been developed which electronically store data representative of braille characters and reproduce that data for a blind reader. All previous systems, however, have suffered from the drawback that they can only reproduce from a few characters to, at most, a single line of braille. It is frequently desirable for both sighted and sightless readers to refer back to previous material on a page or on a previous page. This is especially important, of course, when studying complicated subjects. Examples of this are charts, tables, musical, and mathematical materials. Electronic braille reproduction devices which provide only a single line do not allow a braille reader to easily refer back to previous material or to deal with tabular or multi-line materials. Whereas in a conventional braille book, a blind reader may skim or quickly look for previous material by reading a line or two on a page to determine the location of that material, currently available electronic braille reproduction devices which display only a single line at a time make such reference back to previous material confusing, difficult, and time consuming. It has also been found that a braille reader reads much more slowly when presented with a single line at a time in comparison with the speed at which the full pages of braille books may be read.